Pet door frame



FIG. 1 is a perspective view of a pet door frame showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a side elevational view thereof. 

The ornamental design for a pet door frame, as shown and described. 